1. Field of the Invention
The present invention relates to a fiber reinforced thermoplastic resin sheet, and method and apparatus for manufacturing the same.
2. Description of the Related Art
It is known that a thermoplastic resin having excellent strength and rigidity can be achieved while retaining its desirable molding properties, and that this can be done by adding fibers having a high elastic modulus, thereby producing composite materials which are used for making various kinds of structural members for which light weight, high rigidity, and high impact strength are required. In general, these materials are formed into given shapes after being heated above the melting point of the thermoplastic resins contained as the matrix. Particularly, materials in the shape of plates or sheets are called stampable sheets which are suitably formed by press machines and molded into large parts. The stampable sheets have advantageous light weight and low cost due to the advantages of integral molding which avoids the need for a large number of parts and assembling steps. Therefore, such stampable sheets are applied to structural parts of automobiles, such as a bumper beams, seat backs, rear packages, integrally molded ceilings, and the like. Further, such stampable sheets have been applied to other types of parts as well.
Wet manufacturing like a paper-making technique can be used to make stampable sheets. The stampable sheets may be produced as follows: chopped reinforcing fibers and a thermoplastic resin are dispersed in an aqueous medium (the dispersion step); the resultant dispersion is filtered on a mesh belt to prepare a web-like nonwoven fabric (the web-forming step); and the resultant web is heat-pressed and solidified (the consolidating step). This technique is disclosed in, for example, Japanese Examined Patent Publication Nos. 55-9119 and 2-48423, Japanese Unexamined Patent Publication No. 60-158227, and the like.